Siftproof bottom in paper bags



Aug. 28, 1934. J L S I 1,971,625

SIFTPRQOF BOTTOM IN PAPER BAGS Filed Jan. 22, 1934 .2710 @073/1' 747776,: 1.. Ji/wu Pagentecl Aug. 28, 1934 SIFTPROOF BOTTOM IN PAPER BAGS James L. Shively, Camas,

Crown Willamette Paper Wash., assignor to Company, San

Francisco, Calif., a corporation of Delaware Application January 22,

4 Claims.

Myfi invention relates to the forming of the bottoms of paper bags intended for holding powdery or flufiy material; particularly carbon black, the packed bag of which is afterwards greatly reduced in bulk by compression.

It is necessary that the bottoms of these bags be made sift-tight, so as to prevent blowing out of the powdery material during compression of the pack in the press box. There is also a tendency to blow out the powdery contents of a bag not formed with a sift-proof bottom in the handling of the packed bag.

An essential requirement, however, also is that the cost of manufacture of this type, of bag be low; hence the operations involved in the makq ing of a sift-proof bagmust be simple.

Further, since the parts forming-the bottom are pasted together, it is also essential that the strip of paste applied for that purpose be pre- 2 vented from exuding over adjacent surface portions of the bag; for, since these bags are rapidly made by a machine and are stacked as made, if paste exudes and gets onto contacting surface portions of other bags, the bags will be stuck together more or less, causing a delay, and probable tearing of some of the bags in separating them from each other.

The object of my invention is to attain said essential features; namely, to provide a bag which has a sift-proof bottom and which is also inexpensive to make; and further to prevent the strips of paste, applied for pasting the bottom forming parts together, from spreading out on to adjacent portions of the bag.

The construction of my improved bag bottom is illustrated in the accompanying drawing, in which;

Fig. 1 shows the bag tube slitted at the bottom 'end for producing the bottom forming 40 parts;

Fig. 2 shows the bottom parts folded to form angular folds h, h and fiaps i, i;

Fig. 3 illustrates the folding of the flap 1' over on the crease q in the further step of making my.

bag bottom; 1

Fig. 4 illustrates the folding of the flap 1'' over the flap 1' on the crease q and the final pasting down of the parts, in completing my bag bottom; and

Fig. 5 shows, on larger scale, a portion of my improved bag bottom as shown in Fig. 4, with parts of the sheet forming the folds of the bottom forming portions torn away' to bring out the new results attained by my improvement.

The bottom forming portions of my bag-tube 1c 1934, Serial No. 707,748

are formed to produce the angular folds h, h terminating in lateral fiaps i, 2". The slits 7', 7" of the bag-tube k are short, and located so as to make the angular folds h, it very wide. m, m, m2 indicate the strips of paste applied on the folds h, h 60 and the flaps i, i'.

The outer edges of the paste strips m, m and m2 on the flaps 2, i do not extend to the outer edges of said flaps, and the said paste lines have jogs m3 at the corners 'n, n and n, 11. leaving safety margins 22. On the angular folds h and h' the paste lines extend outward from lines which, if drawn, would connect the corners n and n (Fig. 2)

When the angular folds h, h of my bag bottom are folded over on the line q and pasted down, the corners n, n will lie in the upper and lower paste strips m, m2, as illustrated by Fig. 3. Thus there is no possibility of any sifting at the corners n, n. The bag bottom is then finished by folding h and h over on the line q and pressing the flap 2" down firmly, as shown in Fig. 4. The jogs m3 in the paste lines at'the corners n, n, paralleling the edges s, s of the bottom forming folds h, h, not only hold the later more tightly to the adjacent portions of h and h, but also, by filling up the margins 2'2 (Fig. 3), seal up the corners n.

The overlapping of the corner portions n, n on the corner portions n, n, and securing of the former firmly pasted down to the fiap i also con tributes to making the corners n, n sift-proof.

This fact is illustrated by Fig. 5. The lower corner of the overlying fiap i is shown torn away, and the marks of the paste strips 112. and m2 are exposed. It will be noted that the corners n, n are completely covered and sealed, and that the spreading of the paste in the jogged paste line m2 at the corners n, n seals any sift opening at those places.

Further, referring to Fig. 2, it will be noted that the angular folds h and h of my bag are much Wider than the corresponding angular folds of the old type bag bottoms; with the result that the distance of the corners n and n from the lines q and q respectively is greater than the distance of the corresponding corners from the corresponding lines respectively of ordinary bag bottoms. Since these distances represent the shortest paths which the contents of the bags could follow in order to sift out at the corners as previously mentioned, the wide angular folds h and h ofmy bag supplement the jogged paste .lines 12 on the bottom forming parts, by minimizing the tendency for sifting'to take place at the corners n, n.

My improved bag bottom structure may be used on either a single ply or two ply bag.

I claim:

1. The method of making a sift-proof bag bottom which consists in forming the bottom tubeend with angular folds terminating in lateral flaps, and pasting said folds and their flaps down by strips of paste extending transversely across said folds and flaps, the lines of said strips of paste extending across said flaps and folds and having jogs on the folds at the edges of the latter adjacent the said flaps, whereby the lines of said strips are outwardly offset, the outer edges of said strips being spaced from the edges of said flaps and said folds.

2. The method of making a sift-proof bag bottom which consists in forming the bottom tubeend with .wide angular folds terminating in lateral flaps, the angular edges of said folds arranged to overlap each other, and pasting said folds and their flaps down one over the other by strips of paste extending transversely across said folds and flaps, the lines of said strips of paste extending across said flaps and folds and having jogs on the folds at the edges of the latter adjacent the said flaps, whereby the lines of said strips are outwardly offset, the outer edges of said strips being spaced from the edges of said flaps and said folds.

3. A sift-proof bag bottom having the bottom tube end formed with angular folds terminating in lateral flaps and pasted down by strips of paste extending transversely across said folds and flaps, the lines of said strips of paste extending across said flaps and folds and having jogs on the folds at the edges of the latter adjacent the said flaps, whereby the lines of said strips are outwardly offset, the outer edges of said strips being spaced from the edges of said flaps and said folds.

4. .A sift-proof bag bottom having the bottom tube end formed with wide angular folds terminating in lateral flaps, the angular edges of said folds overlapping each other and pasted down one over the other by strips of paste extending transversely across said folds and flaps, the lines of said strips of paste extending across said flaps and folds and having jogs on the folds at the edges of the latter adjacent the said flaps, whereby the lines of said strips are outwardly offset, the'outer edges of said strips being spaced from the edges of said flaps and said folds.

JANIES L. SHIVELY. 

